As semiconductor circuits continue to increase in complexity, so does their power consumption, and consequently, the amount of heat that is generated. Conventional semiconductor circuits are formed on a die. The die and a lead frame to electrically connect to the circuits are embedded in a an insulating plastic or ceramic package.
Traditionally, a heat sink is used to cool the package. The heat sink is typically configured with a mounting base and perpendicular, or parallel fins. The mounting base can be attached to the package using thermally conductive adhesives, conformable, thermally conductive adhesive tapes, or conformable, thermally conductive liquids or greases, with or without pressure to form a thermally conductive joint.
In a traditional semiconductor package, the heat path is, indirectly, from the die, through the package, through the thermal joint, through the heat sink base, and finally into the fins where the heat can be dissipated into a surrounding environment by convection or radiative cooling.
There are several problems with such traditional semiconductor packages. A substantial portion of the heat path is through the package material, or other laminate layers, such as adhesives, which are usually poor conductors of heat. In addition, the differences between the thermal expansion characteristics of the package and the heat sink can warp the components to varying degrees. The warped components mechanically stress the package and tend to decrease the effectiveness of the bond.
Therefore, it is desired to improve the reliability and performance of semiconductor package cooling techniques. In addition, it is desired that the improved packaging techniques reduce the size, weight, cost, number of parts, and the number of manufacturing steps used to assemble the package.